Ireland train during the Captain’s Run at the Principality Stadium on Friday.
Photograph: Billy Stickland/INPHO/Rex/Shutterstock

Warren Gatland once reflected on Wales’s capacity to sabotage the future by focusing on the past. “They prefer to regurgitate the Chateaubriand of the 1970s rather than sample the fish head soup of the 1990s,” he said. “Reality has hit home but, 20 years on, they still cannot face it.”

He was speaking on the eve of a grand slam match – in 1999 when England came to Wembley and were mugged by Scott Gibbs and Neil Jenkins. Gatland was Ireland’s head coach then but, 20 years on, he presides over his 50th and final Six Nations match with Wales having injected the country with an invigorating dose of reality.

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That it is Ireland who stand in Gatland’s way of a third grand slam adds to the occasion. In the past 12 years it has been the match against Ireland that has generated the greatest heat in the buildup, although this week has been relatively quiet with only the customary dispute over the roof, which will be open at Ireland’s insistence, following on from Johnny Sexton querying whether Wales were getting ahead of themselves.

Initially with Wales Gatland was at his most spiky before facing Ireland, once saying they were the country his players most disliked. Time and success have relaxed him and this week he drenched them with praise: the barbs have tended to come the other way in recent years with Gatland described as “having the intellectual capacity of a tub of Flora” and being “as rational as a menopausal warthog”while the Ireland flanker Sean O’Brien, restored to the side for Saturday, questioned his coaching credentials after the 2017 Lions tour to New Zealand even though he had become only their second coach, after Carwyn James, not to lose a Test series there.

If Gatland once felt the need to unsettle the opposition to camouflage deficiencies in his own team, he does not now, tending to be at his tartest after a match. That is down to the way he has influenced a nation that tended to be at its most vulnerable after it had been successful: before him Wales had won the title in 1988, 1994 and 2005 but within a year the coaches had gone. Gatland himself was under pressure in 2010-11, two years after winning the grand slam. The Welsh Rugby Union might have sacked him after a poor run but its chief executive then, Roger Lewis, gave him a new contract. The fear for the governing body now is what happens when Gatland leaves after the World Cup with his achievements atop a flimsy base.

The Ireland head coach, Joe Schmidt, is also preparing for his final Six Nations match. Like Gatland he has enjoyed considerable success since taking over in 2013 but he was already part of a successful system with Leinster and Ireland’s domestic game is far healthier than in Wales. Just as Manchester United supporters fretted about the departure of Sir Alex Ferguson, it is the same in Wales given Gatland’s capacity to make his players feel that nothing is beyond them.

If Ireland were meeting Wales on paper, they would be clear favourites to win. They have become ruthlessly efficient under Schmidt, losing two of their past 22 Tests, with New Zealand among their victims. All four of their provinces are involved in the knockout stages in Europe at the end of the month while not one Welsh region is.

They have recovered from the opening weekend home defeat by England, when they failed to react in a game played on their opponents’ terms, persisting with the familiar. They choked France into submission, dominating and using penalties to drive lineouts, the source of three of their four tries. Wales, whose lineout has been their weakest feature this tournament, need to be as disciplined as they were against England last month when they conceded three penalties and had to defend only one lineout.

Matches between Wales and Ireland, two teams which in the 1990s tended to collapse at the merest puff of wind, have become known for their unremitting ferocity. The latest instalment, which features 17 Lions among the starters, will be no different. The breakdown will be its crucible with Wales now clearing out more effectively than they did in Dublin a year ago, the last time they lost.

The Gatland factor outweighs paper. As his captain, Alun Wyn Jones, said on Friday “ he came in with one [grand slam] and it would be nice for him to leave with one.” He has rarely lost as a coach on a big occasion, the 2011 World Cup semi-final against France the most notable example when Wales lost by a point after playing with 14 men for an hour but, whatever the result, his record – Wales were 10th in the world when he arrived and have the chance to replace Ireland in second on Saturday – has ensured that the Chateaubriand of the 1970s is back on the menu; and that when the past is invoked, his era will be the first reference.